In the practice of diagnostic medicine, it is often necessary or desirable to perform a biopsy, or to sample selected tissue from a living patient for medical evaluation. Cytological and histological studies of the biopsy sample can then be performed as an aid to the diagnosis and treatment of disease. Biopsies can be useful in diagnosing and treating various forms of cancer, as well as other diseases in which a localized area of affected tissue can be identified.
Biopsies are routinely performed on tissue using a needle set, which typically includes a stylet with a pointed tip and a notch defined near its distal end. The stylet is slidably disposed within a cannula so that the notch can be alternately exposed or covered. Typically, a hub is connected to the proximal end of each needle. Such needle sets are used with or incorporated in various forms of biopsy devices, such as the single action and double action biopsy devices. One such needle set is incorporated into the single action biopsy device shown in FIGS. 1-4.
Referring to FIGS. 1-4, single action biopsy device 20 includes an outer hollow needle 22 defining a lumen 24 therethrough. A stylet 26 is slidingly disposed within lumen 24 and is moveable relative to outer needle 22. A first or distal end 28 of stylet 26 is provided with a tissue cutting-point 30 and a cavity 32 adjacent to first end 28 for receiving tissue samples. Stylet 26 is slidable relative to outer needle 22 between a first or retracted position (FIG. 3) and a second or extended position (FIG. 2).
In the first position, stylet 26 is retracted within lumen 24 so that outer needle 22 covers cavity 32. In the second position, the first end 28 of stylet 26 is extended away from outer needle 22 to expose cavity 32 to tissues at the biopsy site.
During a biopsy procedure, device 20 will be positioned with the cavity 32 at the targeted site for the biopsy. Stylet 26 is momentarily driven into the tissue far enough to expose cavity 32. Tissue then prolapses into cavity 32. The device is then fired to advance outer needle 22 along stylet 26 to cover cavity 32. This forward movement of outer needle 22 severs the prolapsed tissue to obtain a tissue sample, which becomes trapped in cavity 32 of stylet 26. With outer needle 22 blocking the opening of cavity 32, biopsy device 20 is then withdrawn from the target site, carrying the sample within cavity 32. To collect the biopsy sample, outer needle 22 is once again retracted to expose cavity 32 of stylet 26. The procedure may be repeated several times until satisfactory samples have been obtained.
The firing mechanism 40 for such known single action biopsy devices is shown in FIG. 4. Firing mechanism 40 includes a housing 27 having finger grips 41 and 42. An actuator 43 is operatively engaged with both the stylet 26 and outer needle 22. Actuator 43 includes a gripping portion 44 and a drive mechanism 45. Drive mechanism 45 operates to depress a drive carriage 46 against the action of a spring 35. Housing 27 includes a resilient latch 36 that engages an underside 47 of the carriage 46 in the retracted position. Latch 36 is released by forward movement of the drive mechanism 45 so that the spring 35 urges carriage 46 outwardly, which in turn thrusts outer needle 22 over the sampling cavity 32 of the stylet 26. Cover 49 snap-fits over housing 27 to protect spring 35 and the sliding engagement between carriage 46 and housing 27 from debris and interference.
Double action biopsy devices also employ similar needle sets. In a double action biopsy device, movement of inner and outer needles 26, 22 to capture a sample occurs almost instantaneously by means of a firing mechanism engaged with proximal ends 29 of needles 26, 22. A double action biopsy device is disclosed in U.S. Pat. No. 5,538,010.
While these single and double action biopsy devices are widely used, a basic problem remains in the field of biopsy, which is the need to obtain a sufficient amount of sample tissue. One potential cause of the problem is that as the outer needle passes over the tissue cavity, the outer needle has a tendency to push the tissue away from the cavity. This results in samples that are inferior in quality or too small, which precludes the pathologist from conclusively determining whether disease is present, and if so, to what extent it has progressed. The pathologist must then issue an inconclusive diagnostic report. This causes the physician to recall the patient and attempt another needle biopsy, or in some situations, the patient is scheduled for a more invasive, traumatic and expensive procedure such as an open surgical biopsy.
The challenge has been to consistently obtain sufficient tissue volume and quality tissue cores, regardless of tissue type, to meet the needs of the pathologist so that a conclusive diagnosis can be achieved. Therefore, a need remains for a device that can consistently achieve this result.